Epi

Test Sensitivity

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Test Sensitivity, False Negative Rate

  • Definition
  1. Screening Test's ability to identify true disease
  2. A Test with high sensitivity has few false negatives
  3. Independent of disease Prevalence in the community
  4. Sensitive Tests allow user to rule out a condition (mnemonic "SNout")
  • Calculation
  1. Test Sensitivity
    1. True positive tests per total affected patients tested
    2. Test Sensitivity = P(positive test | disease)
      1. Where P (A | B) = Probability of A given B
    3. Expressed as a percentage
  2. False Negative Rate
    1. True cases missed by the Screening Test (test negative despite presence of condition)
    2. False Negative Rate = 1 - Test Sensitivity
  1. Patients with known Crohn's Disease tested: 45
  2. Patients with known Crohn's Disease who have a positive test: 36
  3. Sensitivity = 36/45 or 80%